Construction of initial national quasi-geoid model VIGAC2017, first step to national spatial reference system in Vietnam
Keywords:Global quasi-geoid, local quasi-geoid, mixed quasi-geoid, orientation of ellipsoid
84 reference ellipsoid. However, usage of the broadcast satellite messages doest not give high accuracy in determination of national quasi-geoid heights. Based on the determined geopotential of the Hon Dau local geoid and constructed initial mixed quasi-geoid model VIGAC2014, this scientific article presents results of building of initial national quasi-geoid model VIGAC2017. Used data consisting of geodetic coordinates B, L, H of 164 first and second orders benchmarks of the national leveling networks was obtained from GPS data processing in ITRF according to global WGS-84 ellipsoid with satellite ephemeris accuracy at level of ± 2,5 cm, and the initial mixed quasi-geoid model VIGAC2014 was constructed from the EGM2008 model. The orientation of the WGS-84 ellipsoid was accomplished under conditions of it’s best fitting to the Hon Dau local quasi-geoid and the parallelism of its axes to the corresponding axes of the national WGS-84 reference ellipsoid allows get national quasi-geoid heights and coordinate transformation parameters that have been used for conversion of the mixed quasi-geoid heights from the VIGAC2014 quasi-geoid model to the initial national quasi-geoid model VIGAC2017.
Along withquasi-geoid heights which were obtained from the initial national quasi-geoid model VIGAC2017, an estimation of the accuracy of differences ( ) shows that quasi-geoid heights have the accuracy at the level of ± 6,2 cm. Apart from that determination of seven coordinate transformation parameters leads to the building of the initial national spatial reference system in Vietnam.
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